Hydraulic engine mounts may be attached to a vehicle body or other suitable vehicle component to attenuate engine noise, vibration and harshness (NVH) to acceptable thresholds. Hydraulic engine mounts may be provided in different configurations to allow engine mount performance under a wide range of vehicle operating conditions. For example, an engine mount may be designed to provide hydraulic damping under both idle engine and motive engine conditions. As such, performance requirements of the engine mount may vary, introducing competing requirements. For example, high damping needed during engine motive conditions may increase incidence of parasitic noise, which is structure borne rather than airborne. In this case, the parasitic noise may not become apparent until prior to vehicle launch. Additional changes made to the engine mount during late stages in production may be costly and detrimental to vehicle performance.
During engine operation, a decoupler in an engine mount may come in contact with a channel plate producing low amplitude noise, with peak to peak amplitude of at least 2 mm. Another problem in an engine mount is cavitation phenomena which occurs when a local fluid pressure falls below fluid vapor pressure as the fluid flows through the engine mount producing gas bubbles. The generated gas bubbles may grow larger and later collapse rapidly against internal walls of the engine mount causing pitting or destruction of the walls and other engine components. Further, cavitation may be accompanied by production of high amplitude noise, with peak to peak amplitudes of at least 8 mm.
An example engine mount is disclosed by van den Boom in U.S. Pat. No. 4,199,128. Therein, the engine mount with a main housing containing an elastic wall connected to a force transmitting member formed with an opening fluidly connected to the main housing. Pressure differentials within the engine mount are primarily controlled by fluid transfer between internal chambers via the opening, and deformation of the elastic wall.
However, in the example engine mount disclosed above, it may be difficult to change or adjust engine mount parameters (such as stiffness and damping parameters) once the engine mount has been assembled or during later stages in engine production, prior to vehicle launch. Further, the cavitation phenomena, which often occurs in engine mounts and other engine components, may be particularly prevalent in such a design.
The inventors herein have recognized the various issues discussed above, and developed a hydraulic engine mount to at least partially address them. In one example, a method for manufacturing a hydraulic engine mount, may comprise: inserting air filled dissolving caps into a chamber below a rubber damper; and filling the chamber with a fluid and sealing the chamber. In this way, one method for manufacturing the hydraulic engine mount may be used to reduce pressure differentials across the engine mount to reduce or minimize cavitation while addressing noise, vibration and harshness (NVH) issues.
For example, an air filled dissolving gel cap may be inserted into a chamber of the hydraulic engine mount, the chamber filled with glycol solution and sealed. The gel cap may dissolve in the glycol solution and release air bubbles to reduce pressure differentials across the engine mount. By releasing air bubbles in the chamber, pressure differentials across the hydraulic engine mount may be reduced or minimized. In this way, cavitation occurrence during engine operation may be addressed while reducing undesirable noise and vibration.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.
FIG. 1 is shown to scale, although other relative dimensions may be used, if desired.